A recent article in the Sydney Morning Herald talks about using slides, particularly those in PowerPoint format. The key quote for me is, "It is effective to speak to a diagram, because it presents information in a different form. But it is not effective to speak the same words that are written, because it is putting too much load on the mind and decreases your ability to understand what is being presented."

I think it nicely explains why so many people get so frustrated by seeing a talk where someone just reads the text on their slides, almost word for word.

Another annoyance factor in reading slides aloud that many people don't think of: the audience can read faster than you can talk. So most of the time, when you put up a slide of text, the audience will have read the text and is just waiting for you to catch up to your own text.

It is tough to get rid of text completely. I am guilty of using text slides all the time when I lecture. I console myself that sometimes, there is a legitimate teaching reason to put up text slides: because students need to be able to see the correct spelling of technical words. If I were to just say, "allele," I have little confidence that students would be able to figure out the right spelling from the pronunciation alone. (There are various pronunciations, but the mode seems to be "a-leel," not, as the spelling might lead you to think, "ah-lel-lay.")

When I do have a text slide, another thing I try to do is not to read it verbatim. I try to put the same information in a different way. Use examples. Elaborate. Often, I go on talking on a point much longer than the slide is up, so that people will get bored at the slide and their attention focuses back on me.

It is a constant challenge to presenters, including myself, to use more pictures -- perhaps only pictures. And high quality picture. Assuming, of course, that they need visual aids at all (see Part 3).